Using molecular sieve ssz-63 for reduction of oxides of nitrogen in a gas stream

ABSTRACT

The present invention relates to new crystalline molecular sieve SSZ-63 prepared using N-cyclodecyl-N-methyl-pyrrolidinium cation as a structure-directing agent, methods for synthesizing SSZ-63 and processes employing SSZ-63 in a catalyst.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to new crystalline molecular sieveSSZ-63, a method for preparing SSZ-63 usingN-cyclodecyl-N-methyl-pyrrolidinium cation as a structure directingagent and the use of SSZ-63 in catalysts for, e.g., hydrocarbonconversion reactions.

[0003] 2. State of the Art

[0004] Because of their unique sieving characteristics, as well as theircatalytic properties, crystalline molecular sieves and zeolites areespecially useful in applications such as hydrocarbon conversion, gasdrying and separation. Although many different crystalline molecularsieves have been disclosed, there is a continuing need for new zeoliteswith desirable properties for gas separation and drying, hydrocarbon andchemical conversions, and other applications. New zeolites may containnovel internal pore architectures, providing enhanced selectivities inthese processes.

[0005] Crystalline aluminosilicates are usually prepared from aqueousreaction mixtures containing alkali or alkaline earth metal oxides,silica, and alumina. Crystalline borosilicates are usually preparedunder similar reaction conditions except that boron is used in place ofaluminum. By varying the synthesis conditions and the composition of thereaction mixture, different zeolites can often be formed.

SUMMARY OF THE INVENTION

[0006] The present invention is directed to a family of crystallinemolecular sieves with unique properties, referred to herein as“molecular sieve SSZ-63” or simply “SSZ-63”. Preferably, SSZ-63 isobtained in its silicate, aluminosilicate, titanosilicate,germanosilicate, vanadosilicate or borosilicate form. The term“silicate” refers to a molecular sieve having a high mole ratio ofsilicon oxide relative to aluminum oxide, preferably a mole ratiogreater than 100, including molecular sieves comprised entirely ofsilicon oxide. As used herein, the term “aluminosilicate” refers to amolecular sieve containing both alumina and silica and the term“borosilicate” refers to a molecular sieve containing oxides of bothboron and silicon.

[0007] In accordance with this invention, there is provided an improvedprocess for the reduction of oxides of nitrogen contained in a gasstream in the presence of oxygen wherein said process comprisescontacting the gas stream with a zeolite, the improvement comprisingusing as the zeolite a zeolite having a mole ratio greater than about 15of an oxide of a first tetravalent element to an oxide of a secondtetravalent element different from said first tetravalent element,trivalent element, pentavalent element or mixture thereof and having,after calcination, the X-ray diffraction lines of Table II. The zeolitemay contain a metal or metal ions (such as cobalt, copper or mixturesthereof) capable of catalyzing the reduction of the oxides of nitrogen,and may be conducted in the presence of a stoichiometric excess ofoxygen. In a preferred embodiment, the gas stream is the exhaust streamof an internal combustion engine.

BRIEF DESCRIPTION OF THE DRAWING

[0008] The drawing is a powder X-ray diffraction pattern of calcinedSSZ-63.

DETAILED DESCRIPTION OF THE INVENTION

[0009] The present invention comprises a family of crystalline, largepore molecular sieves designated herein “molecular sieve SSZ-63” orsimply “SSZ-63”. As used herein, the term “large pore” means having anaverage pore size diameter greater than about 6.0 Angstroms, preferablyfrom about 6.5 Angstroms to about 7.5 Angstroms.

[0010] While not wishing to be bound by any theory, it is believed thatthe crystal structure of SSZ-63 consists of two polymorphs of zeolitebeta. Typical zeolite beta (BEA*) has a crystal structure consisting ofabout a 50/50 combination of two polymorphs, polymorph A and polymorphB. It is believed that the crystal structure of SSZ-63 consists of about60-70% of a beta polymorph referred to herein as beta-C (Higgins) withthe remainder being beta polymorph B. Beta polymorph C (Higgins) isdifferent from beta polymorph C. The structure of polymorph C (Higgins)has been postulated in the literature, but it is believed that polymorphC (Higgins) has heretofore not been made. A discussion of polymorph C(Higgins) can be found in Higgins et al, “The framework Topology ofZeolite Beta”, Zeolites, 1988, vol. 8, pp. 446-452, with a correction atHiggins et al., “The Framework Topology of Zeolite Beta—A Correction”,Zeolites, 1989, vol. 9, p. 358.

[0011] In preparing SSZ-63, N-cyclodecyl-N-methyl-pyrrolidinium cationis used as a structure directing agent (“SDA”), also known as acrystallization template. In general, SSZ-63 is prepared by contactingan active source of one or more oxides selected from the groupconsisting of monovalent element oxides, divalent element oxides,trivalent element oxides, tetravalent element oxides and pentavalentelements with the N-cyclodecyl-N-methyl-pyrrolidinium cation SDA.

[0012] SSZ-63 is prepared from a reaction mixture having the compositionshown in Table A below. TABLE A Reaction Mixture Typical PreferredYO₂/W_(a)O_(b) >15 30-70 OH—/YO₂ 0.10-0.50 0.20-0.30 Q/YO₂ 0.05-0.500.10-0.20 M_(2/n)/YO₂ 0.02-0.40 0.10-0.25 H₂O/YO₂ 30-80 35-45

[0013] where Y, W, Q, M and n are as defined above, and a is 1 or 2, andb is 2 when a is 1 (i.e., W is tetravalent) and b is 3 when a is 2(i.e., W is trivalent).

[0014] In practice, SSZ-63 is prepared by a process comprising:

[0015] (a) preparing an aqueous solution containing sources of at leastone oxide capable of forming a crystalline molecular sieve and aN-cyclodecyl-N-methyl-pyrrolidinium cation having an anionic counterionwhich is not detrimental to the formation of SSZ-63;

[0016] (b) maintaining the aqueous solution under conditions sufficientto form crystals of SSZ-63; and

[0017] (c) recovering the crystals of SSZ-63.

[0018] Accordingly, SSZ-63 may comprise the crystalline material and theSDA in combination with metallic and non-metallic oxides bonded intetrahedral coordination through shared oxygen atoms to form across-linked three dimensional crystal structure. The metallic andnon-metallic oxides comprise one or a combination of oxides of a firsttetravalent element(s), and one or a combination of a trivalentelement(s), pentavalent element(s), second tetravalent element(s)different from the first tetravalent element(s) or mixture thereof. Thefirst tetravalent element(s) is preferably selected from the groupconsisting of silicon, germanium and combinations thereof. Morepreferably, the first tetravalent element is silicon. The trivalentelement, pentavalent element and second tetravalent element (which isdifferent from the first tetravalent element) is preferably selectedfrom the group consisting of aluminum, gallium, iron, boron, titanium,indium, vanadium and combinations thereof. More preferably, the secondtrivalent or tetravalent element is aluminum or boron.

[0019] Typical sources of aluminum oxide for the reaction mixtureinclude aluminates, alumina, aluminum colloids, aluminum oxide coated onsilica sol, hydrated alumina gels such as Al(OH)₃ and aluminum compoundssuch as AlCl₃ and Al₂(SO₄)₃. Typical sources of silicon oxide includesilicates, silica hydrogel, silicic acid, fumed silica, colloidalsilica, tetra-alkyl orthosilicates, and silica hydroxides. Boron, aswell as gallium, germanium, titanium, indium, vanadium and iron, can beadded in forms corresponding to their aluminum and silicon counterparts.

[0020] A source zeolite reagent may provide a source of aluminum orboron. In most cases, the source zeolite also provides a source ofsilica. The source zeolite in its dealuminated or deboronated form mayalso be used as a source of silica, with additional silicon added using,for example, the conventional sources listed above. Use of a sourcezeolite reagent as a source of alumina for the present process is morecompletely described in U.S. Pat. No. 5,225,179, issued Jul. 6, 1993 toNakagawa entitled “Method of Making Molecular Sieves”, the disclosure ofwhich is incorporated herein by reference.

[0021] Typically, an alkali metal hydroxide and/or an alkaline earthmetal hydroxide, such as the hydroxide of sodium, potassium, lithium,cesium, rubidium, calcium, and magnesium, is used in the reactionmixture; however, this component can be omitted so long as theequivalent basicity is maintained. The SDA may be used to providehydroxide ion. Thus, it may be beneficial to ion exchange, for example,the halide to hydroxide ion, thereby reducing or eliminating the alkalimetal hydroxide quantity required. The alkali metal cation or alkalineearth cation may be part of the as-synthesized crystalline oxidematerial, in order to balance valence electron charges therein.

[0022] The reaction mixture is maintained at an elevated temperatureuntil the crystals of the SSZ-63 are formed. The hydrothermalcrystallization is usually conducted under autogenous pressure, at atemperature between 100° C. and 200° C., preferably between 135° C. and160° C. The crystallization period is typically greater than 1 day andpreferably from about 3 days to about 20 days.

[0023] Preferably, the molecular sieve is prepared using mild stirringor agitation.

[0024] During the hydrothermal crystallization step, the SSZ-63 crystalscan be allowed to nucleate spontaneously from the reaction mixture. Theuse of SSZ-63 crystals as seed material can be advantageous indecreasing the time necessary for complete crystallization to occur. Inaddition, seeding can lead to an increased purity of the productobtained by promoting the nucleation and/or formation of SSZ-63 over anyundesired phases. When used as seeds, SSZ-63 crystals are added in anamount between 0.1 and 10% of the weight of silica used in the reactionmixture.

[0025] Once the molecular sieve crystals have formed, the solid productis separated from the reaction mixture by standard mechanical separationtechniques such as filtration. The crystals are water-washed and thendried, e.g., at 90° C. to 150° C. for from 8 to 24 hours, to obtain theas-synthesized SSZ-63 crystals. The drying step can be performed atatmospheric pressure or under vacuum.

[0026] SSZ-63 as prepared has a mole ratio of an oxide selected fromsilicon oxide, germanium oxide and mixtures thereof to an oxide selectedfrom aluminum oxide, gallium oxide, iron oxide, boron oxide, titaniumoxide, indium oxide, vanadium oxide and mixtures thereof greater thanabout 15; and has, after calcination, the X-ray diffraction lines ofTable II below. SSZ-63 further has a composition, as synthesized (i.e.,prior to removal of the SDA from the SSZ-63) and in the anhydrous state,in terms of mole ratios, shown in Table B below. TABLE B As-SynthesizedSSZ-63 YO₂/W_(c)O_(d) >15 M_(2/n)/YO₂ 0.01-0.03 Q/YO₂ 0.02-0.05

[0027] where Y, W, c, d, M, n and Q are as defined above.

[0028] SSZ-63 can be made essentially aluminum free, i.e., having asilica to alumina mole ratio of ∞. A method of increasing the mole ratioof silica to alumina is by using standard acid leaching or chelatingtreatments. However, essentially aluminum-free SSZ-63 can be synthesizeddirectly using essentially aluminum-free silicon sources as the maintetrahedral metal oxide component, if boron is also present. The boroncan then be removed, if desired, by treating the borosilicate SSZ-63with acetic acid at elevated temperature (as described in Jones et al.,Chem. Mater., 2001, 13, 1041-1050) to produce an all-silica version ofSSZ-63. SSZ-63 can also be prepared directly as a borosilicate. Ifdesired, the boron can be removed as described above and replaced withmetal atoms by techniques known in the art to make, e.g., analuminosilicate version of SSZ-63. SSZ-63 can also be prepared directlyas an aluminosilicate.

[0029] Lower silica to alumina ratios may also be obtained by usingmethods which insert aluminum into the crystalline framework. Forexample, aluminum insertion may occur by thermal treatment of thezeolite in combination with an alumina binder or dissolved source ofalumina. Such procedures are described in U.S. Pat. No. 4,559,315,issued on Dec. 17, 1985 to Chang et al.

[0030] It is believed that SSZ-63 is comprised of a new frameworkstructure or topology which is characterized by its X-ray diffractionpattern. SSZ-63, as-synthesized, has a crystalline structure whose X-raypowder diffraction pattern exhibit the characteristic lines shown inTable I and is thereby distinguished from other molecular sieves. TABLEI As-Synthesized SSZ-63 2 Theta^((a)) d-spacing (Angstroms) RelativeIntensity (%) 7.17 12.32 W 7.46 11.84 W 7.86 11.24 W 8.32 10.62 W 21.424.15 M 22.46 3.96 VS 22.85 3.89 W 25.38 3.51 W 27.08 3.29 W 29.62 3.01 W

[0031] Table IA below shows the X-ray powder diffraction lines foras-synthesized SSZ-63 including actual relative intensities. TABLE IA 2Theta^((a)) d-spacing (Angstroms) Relative Intensity (%) 7.17 12.32 5.17.46 11.84 13.5 7.86 11.24 10.2 8.32 10.62 4.7 13.38 6.61 1.7 17.20 5.151.4 18.21 4.87 2.0 19.29 4.60 1.5 21.42 4.15 15.7 22.46 3.96 100.0 22.853.89 6.9 25.38 3.51 6.7 26.02 3.42 1.8 27.08 3.29 12.3 28.80 3.10 3.229.62 3.01 8.5 30.50 2.93 2.9 32.88 2.72 1.4 33.48 2.67 5.7 34.76 2.581.8 36.29 2.47 1.6 37.46 2.40 1.3

[0032] After calcination, the SSZ-63 molecular sieves have a crystallinestructure whose X-ray powder diffraction pattern include thecharacteristic lines shown in Table II: TABLE II Calcined SSZ-63 2Theta^((a)) d-spacing (Angstroms) Relative Intensity (%) 7.19 12.29 M7.42 11.91 VS 7.82 11.30 VS 8.30 10.64 M 13.40 6.60 M 21.46 4.14 W 22.503.95 VS 22.81 3.90 W 27.14 3.28 M 29.70 3.06 W

[0033] Table IIA below shows the X-ray powder diffraction lines forcalcined SSZ-63 including actual relative intensities. TABLE IIA 2Theta^((a)) d-spacing (Angstroms) Relative Intensity (%) 7.19 12.29 27.77.42 11.91 68.5 7.82 11.29 67.0 8.30 10.64 40.1 10.46 8.45 3.1 11.317.82 6.7 13.40 6.60 25.1 14.38 6.16 5.3 14.60 6.06 6.5 21.46 4.14 11.222.50 3.95 100.0 22.81 3.90 13.0 25.42 3.50 9.2 27.14 3.28 19.6 28.803.10 8.2 29.70 3.01 11.0 30.48 2.93 3.3 33.56 2.67 3.9 34.86 2.57 3.336.29 2.47 3.2 37.64 2.39 2.8

[0034] The X-ray powder diffraction patterns were determined by standardtechniques. The radiation was the K-alpha/doublet of copper. The peakheights and the positions, as a function of 2θ where θ is the Braggangle, were read from the relative intensities of the peaks, and d, theinterplanar spacing in Angstroms corresponding to the recorded lines,can be calculated.

[0035] The variation in the scattering angle (two theta) measurements,due to instrument error and to differences between individual samples,is estimated at ±0.20 degrees.

[0036] The X-ray diffraction pattern of Table I is representative of“as-synthesized” or “as-made” SSZ-63 molecular sieves. Minor variationsin the diffraction pattern can result from variations in thesilica-to-alumina or silica-to-boron mole ratio of the particular sampledue to changes in lattice constants. In addition, sufficiently smallcrystals will affect the shape and intensity of peaks, leading tosignificant peak broadening.

[0037] Representative peaks from the X-ray diffraction pattern ofcalcined SSZ-63 are shown in Table II. Calcination can also result inchanges in the intensities of the peaks as compared to patterns of the“as-made” material, as well as minor shifts in the diffraction pattern.The molecular sieve produced by exchanging the metal or other cationspresent in the molecular sieve with various other cations (such as H⁺ orNH₄ ⁺) yields essentially the same diffraction pattern, although again,there may be minor shifts in the interplanar spacing and variations inthe relative intensities of the peaks. Notwithstanding these minorperturbations, the basic crystal lattice remains unchanged by thesetreatments.

[0038] Crystalline SSZ-63 can be used as-synthesized, but preferablywill be thermally treated (calcined). Usually, it is desirable to removethe alkali metal cation by ion exchange and replace it with hydrogen,ammonium, or any desired metal ion. The molecular sieve can be leachedwith chelating agents, e.g., EDTA or dilute acid solutions, to increasethe silica to alumina mole ratio. The molecular sieve can also besteamed; steaming helps stabilize the crystalline lattice to attack fromacids.

[0039] The molecular sieve can be used in intimate combination withhydrogenating components, such as tungsten, vanadium, molybdenum,rhenium, nickel, cobalt, chromium, manganese, or a noble metal, such aspalladium or platinum, for those applications in which ahydrogenation-dehydrogenation function is desired.

[0040] Metals may also be introduced into the molecular sieve byreplacing some of the cations in the molecular sieve with metal cationsvia standard ion exchange techniques (see, for example, U.S. Pat. Nos.3,140,249 issued Jul. 7, 1964 to Plank et al.; 3,140,251 issued Jul. 7,1964 to Plank et al.; and 3,140,253 issued Jul. 7, 1964 to Plank etal.). Typical replacing cations can include metal cations, e.g., rareearth, Group IA, Group IIA and Group VIII metals, as well as theirmixtures. Of the replacing metallic cations, cations of metals such asrare earth, Mn, Ca, Mg, Zn, Cd, Pt, Pd, Ni, Co, Ti, Al, Sn, and Fe areparticularly preferred.

[0041] The hydrogen, ammonium, and metal components can be ion-exchangedinto the SSZ-63. The SSZ-63 can also be impregnated with the metals, orthe metals can be physically and intimately admixed with the SSZ-63using standard methods known to the art.

[0042] Typical ion-exchange techniques involve contacting the syntheticmolecular sieve with a solution containing a salt of the desiredreplacing cation or cations. Although a wide variety of salts can beemployed, chlorides and other halides, acetates, nitrates, and sulfatesare particularly preferred. The molecular sieve is usually calcinedprior to the ion-exchange procedure to remove the organic matter presentin the channels and on the surface, since this results in a moreeffective ion exchange. Representative ion exchange techniques aredisclosed in a wide variety of patents including U.S. Pat. Nos.3,140,249 issued on Jul. 7, 1964 to Plank et al.; 3,140,251 issued onJul. 7, 1964 to Plank et al.; and 3,140,253 issued on Jul. 7, 1964 toPlank et al.

[0043] Following contact with the salt solution of the desired replacingcation, the molecular sieve is typically washed with water and dried attemperatures ranging from 65° C. to about 200° C. After washing, themolecular sieve can be calcined in air or inert gas at temperaturesranging from about 200° C. to about 800° C. for periods of time rangingfrom 1 to 48 hours, or more, to produce a catalytically active productespecially useful in hydrocarbon conversion processes.

[0044] Regardless of the cations present in the synthesized form ofSSZ-63, the spatial arrangement of the atoms which form the basiccrystal lattice of the molecular sieve remains essentially unchanged.

[0045] SSZ-63 can be formed into a wide variety of physical shapes.Generally speaking, the molecular sieve can be in the form of a powder,a granule, or a molded product, such as extrudate having a particle sizesufficient to pass through a 2-mesh (Tyler) screen and be retained on a400-mesh (Tyler) screen. In cases where the catalyst is molded, such asby extrusion with an organic binder, the SSZ-63 can be extruded beforedrying, or, dried or partially dried and then extruded.

[0046] SSZ-63 can be composited with other materials resistant to thetemperatures and other conditions employed in organic conversionprocesses. Such matrix materials include active and inactive materialsand synthetic or naturally occurring zeolites as well as inorganicmaterials such as clays, silica and metal oxides. Examples of suchmaterials and the manner in which they can be used are disclosed in U.S.Pat. No. 4,910,006, issued May 20, 1990 to Zones et al., and U.S. Pat.No. 5,316,753, issued May 31, 1994 to Nakagawa, both of which areincorporated by reference herein in their entirety.

[0047] SSZ-64 may be used for the catalytic reduction of the oxides ofnitrogen in a gas stream. Typically, the gas stream also containsoxygen, often a stoichiometric excess thereof. Also, the SSZ-64 maycontain a metal or metal ions within or on it which are capable ofcatalyzing the reduction of the nitrogen oxides. Examples of such metalsor metal ions include copper, cobalt and mixtures thereof.

[0048] One example of such a process for the catalytic reduction ofoxides of nitrogen in the presence of a zeolite is disclosed in U.S.Pat. No. 4,297,328, issued Oct. 27, 1981 to Ritscher et al., which isincorporated by reference herein. There, the catalytic process is thecombustion of carbon monoxide and hydrocarbons and the catalyticreduction of the oxides of nitrogen contained in a gas stream, such asthe exhaust gas from an internal combustion engine. The zeolite used ismetal ion-exchanged, doped or loaded sufficiently so as to provide aneffective amount of catalytic copper metal or copper ions within or onthe zeolite. In addition, the process is conducted in an excess ofoxidant, e.g., oxygen.

EXAMPLES

[0049] The following examples demonstrate but do not limit the presentinvention.

Example 1

[0050] Synthesis of the Structure-Directing Agent A(N-cyclodecyl-N-methyl-pyrrolidinium cation)

[0051] The anion (X⁻) associated with the cation may be any anion whichis not detrimental to the formation of the zeolite. Representativeanions include halogen, e.g., fluoride, chloride, bromide and iodide,hydroxide, acetate, sulfate, tetrafluoroborate, carboxylate, and thelike. Hydroxide is the most preferred anion.

[0052] The structure-directing agent (SDA)N-cyclodecyl-N-methyl-pyrrolidinium cation was synthesized according tothe procedure described below (see Scheme 1). To a solution ofcyclodecanone (25 gm; 0.16 mol) in 320 ml anhydrous hexane in athree-necked round bottom flask equipped with a reflux condenser and amechanical stirrer, 34 gm of pyrrolidine (0.48 mol) and 48 gm (0.4 mol)anhydrous magnesium sulfate were added. The resulting mixture wasstirred while heating at reflux for five days. The reaction mixture wasfiltered through a fritted-glass funnel. The filtrate was concentratedat reduced pressure on a rotary evaporator to yield 32 gm (96%) of theexpected enamine (1-cyclodec-1-enyl-pyrrolidine) as a reddish oilysubstance. ¹H—NMR and ¹³C—NMR spectra were acceptable for the desiredproduct. The enamine was reduced to the corresponding amine(N-cyclodecyl-pyrrolidine) in quantitative yield via catalytichydrogenation in the presence of 10% Pd on activated carbon at hydrogenpressure of 55 PSI in ethanol.

[0053] Quaternization of N-cyclodecyl-pyrrolidine with methyl iodide(Synthesis of N-cyclodecyl-N-methyl-pyrrolidinium iodide)

[0054] To a solution of 30 gm (0.14 mol.) of N-cyclodecyl-pyrrolidine in250 ml anhydrous methanol in a one liter reaction flask, 30 gm (0.21mol.) of methyl iodide was added. The reaction mixture was mechanicallystirred for 48 hours at room temperature. Then, a 0.5 mole equivalent ofmethyl iodide was added and the mixture was heated to reflux andrefluxed for 30 minutes. The reaction mixture was then cooled down andconcentrated under reduced pressure on a rotary evaporator to give theproduct as a pale yellow solid material. The product was purified bydissolving in acetone and then precipitating by adding diethyl ether.The recrystallization yielded 46 gm (93%) of the pureN-cyclodecyl-N-methyl-pyrrolidinium iodide. ¹H—NMR and ¹³C—NMR wereideal for the product.

[0055] Ion Exchange (Synthesis of N-cyclodecyl-N-methyl-pyrrolidiniumhydroxide)

[0056] N-cyclodecyl-N-methyl-pyrrolidinium iodide (45 gm; 0.128 mol) wasdissolved in 150 ml water in a 500 ml plastic bottle. To the solution,160 gm of Ion-Exchange Resin—OH (BIO RAD® AH1-X8) was added and themixture was stirred at room temperature overnight. The mixture wasfiltered and the solids were rinsed with an additional 85 ml of water.The reaction afforded 0.12 mole of the SDA(N-cyclodecyl-N-methyl-pyrrolidinium hydroxide) as indicated bytitration analysis with 0.1N HCl.

Example 2 Synthesis of Borosilicate SSZ-63

[0057] A 23 cc Teflon liner was charged with 4.9 gm of 0.61M aqueoussolution of N-cyclodecyl-N-methyl-pyrrolidinium hydroxide (3 mmol SDA),1.2 gm of 1M aqueous solution of NaOH (1.2 mmol NaOH) and 5.9 gm ofde-ionized water. To this mixture, 0.06 gm of sodium borate decahydrate(0.157 mmol of Na₂B₄O₇.10H₂O; ˜0.315 mmol B₂O₃) was added and stirreduntil completely dissolved. To this solution, 0.9 gm of CABO-SIL M-5®fumed silica (˜14.7 mmol SiO₂) was added and thoroughly stirred by hand.The resulting gel was capped off and placed in a Parr steel autoclaveand heated in an oven at about 160° C. while tumbling at about 43 rpm.The reaction was monitored by periodically monitoring the pH of the gel,and by looking for crystal growth using scanning electron microscopy(SEM). Once the crystallization was completed, after heating for 12 daysat the conditions described above, the starting reaction gel turned intoa clear liquid layer and a fine powdery precipitate. The mixture wasfiltered through a fritted-glass funnel. The collected solids werethoroughly washed with water and, then, rinsed with acetone (˜20 ml) toremove any organic residues. The solids were allowed to air-dry overnight and, then, dried in an oven at 120° C. for 1hour. The reactionafforded 0.85 gram of SSZ-63. The originality of SSZ-64 was determinedfrom its unique XRD pattern, and by transmission electron microscopyanalysis

Example 3 Conversion of Borosilicate SSZ-63 to Aluminosilicate SSZ-63

[0058] Borosilicate SSZ-63 synthesized as described in Example 2 aboveand calcined as shown in Example 17 below was suspended in 1M solutionof aluminum nitrate nonahydrate (15 ml of 1M Al(NO₃)₃.9H₂O soln./1 gmzeolite). The suspension was heated at reflux for 48 hours. The mixturewas then filtered and the collected solids were thoroughly rinsed withwater and air-dried overnight. The solids were further dried in an ovenat 120° C. for 2 hours.

Example 4 Synthesis of Germanosilicate SSZ-63

[0059] A 23 cc Teflon liner was charged with 4.85 gm of 0.61M aqueoussolution of N-cyclodecyl-N-methyl-pyrrolidinium hydroxide (3 mmol SDA),1.25 gm of 1M aqueous solution of NaOH (1.25 mmol NaOH) and 5.8 gm ofde-ionized water. To this mixture, 0.25 gm of GeO₂ (2.39 mmol) was addedand stirred until completely dissolved. To this solution, 0.7 gm ofCAB-O-SIL M-5® (˜11.4 mmol SiO₂) was added and thoroughly stirred byhand. The resulting gel was capped off and placed in a Parr steelautoclave and heated in an oven at about 160° C. while tumbling at about43 rpm. The reaction was monitored by periodically monitoring the pH ofthe gel, and by looking for crystal growth using scanning electronmicroscopy (SEM). Once the crystallization was completed, after heatingfor six days, the starting reaction gel turned into a clear liquid layerand a fine powdery precipitate. The mixture was filtered through afritted-glass funnel. The collected solids were thoroughly washed withwater and, then, rinsed with acetone (˜20 ml) to remove any organicresidues. The solids were allowed to air-dry over night and, then, driedin an oven at 120° C. for one hour. The reaction afforded 0.73 gram ofSSZ-63.

Examples 5-16 Synthesis of Borosilicate SSZ-63

[0060] SSZ-63 was synthesized at varying SiO₂/B₂O₃ ratios in thestarting synthesis gel. This was accomplished by using the syntheticconditions described in Example 2 keeping everything the same whilechanging the SiO₂/B₂O₃ ratios in the starting gel. This was done bykeeping the amount of CAB-O-SIL M-5® (the source of SiO₂) constant whilevarying the amount of sodium borate decahydrates added in each run.Consequently, varying the amount of sodium borate decahydrates led tovarying the SiO₂/Na ratios in the starting gels. The table below showsthe SiO₂/B₂O₃ and SiO₂/Na ratios and the observed products for each run.Example Crystallization No. SiO₂/B₂O₃ SiO₂/Na Time (days) Products 5 ∞14.7 6 BETA (BEA*) 6 280 13.9 12 SSZ-63 7 140 13.3 12 SSZ-63 8 93 12.712 SSZ-63 9 70 12.1 12 SSZ-63 10 56 11.6 12 SSZ-63 11 47 11.2 12 SSZ-6312 40 10.7 12 SSZ-63 13 31 10 12 SSZ-63 14 23 9 12 SSZ-63 15 19 8.2 12SSZ-63 16 12.6 6.8 12 SSZ-63

Example 17 Calcination of SSZ-63

[0061] The material from Example 3 is calcined in the following manner.A thin bed of material is heated in a muffle furnace from roomtemperature to 120° C. at a rate of 1° C. per minute and held at 120° C.for three hours. The temperature is then ramped up to 540° C. at thesame rate and held at this temperature for five hours, after which it isincreased to 594° C. and held there for another five hours. A 50/50mixture of air and nitrogen is passed over the SSZ-63 at a rate of 20standard cubic feet per minute during heating.

Example 18 NH₄ Exchange

[0062] Ion exchange of calcined SSZ-63 material (as prepared in Example2, and calcined as in Example 17) is performed using NH₄NO₃ to convertthe SSZ-63 from its Na⁺ form to the NH₄ ⁺ form, and, ultimately, the H⁺form. Typically, the same mass of NH₄NO₃ as SSZ-63 is slurried in waterat a ratio of 25-50:1 water to SSZ-63. The exchange solution is heatedat 95° C. for two hours and then filtered. This procedure can berepeated up to three times. Following the final exchange, the SSZ-63 iswashed several times with water and dried. This NH₄ ⁺ form of SSZ-63 canthen be converted to the H⁺ form by calcination (as described in Example17) to 540° C.

Example 19 Constraint Index Determination

[0063] The hydrogen form of the SSZ-63 of Example 2 (after treatmentaccording to Examples 17, 3 and 18) is pelletized at 2-3 KPSI, crushedand meshed to 20-40, and then >0.50 gram is calcined at about 540° C. inair for four hours and cooled in a desiccator. 0.50 Gram is packed intoa ⅜ inch stainless steel tube with alundum on both sides of themolecular sieve bed. A Lindburg furnace is used to heat the reactortube. Helium is introduced into the reactor tube at 10 cc/min. and atatmospheric pressure. The reactor is heated to about 315° C., and a50/50 (w/w) feed of n-hexane and 3-methylpentane is introduced into thereactor at a rate of 8 μl/min. Feed delivery is made via a Brownleepump. Direct sampling into a gas chromatograph begins after ten minutesof feed introduction. The Constraint Index value is calculated from thegas chromatographic data using methods known in the art. SSZ-63 has aConstraint Index of 1.1 after 10 minutes at 315° C. with 87.7% feedconversion. The Constraint Index dropped with time on stream (0.6 at 100minutes) suggesting that SSZ-63 is a large pore molecular sieve.

Example 20 Hydrocracking of n-Hexadecane

[0064] A sample of SSZ-63 as prepared in Example 2 was treated as inExamples 17, 3 and 18. Then a sample was slurried in water and the pH ofthe slurry was adjusted to a pH of ˜10 with dilute ammonium hydroxide.To the slurry was added a solution of Pd(NH₃)₄(NO₃)₂ at a concentrationwhich would provide 0.5 wt. % Pd with respect to the dry weight of themolecular sieve sample. This slurry was stirred for 48 hours at 100° C.After cooling, the slurry was filtered through a glass frit, washed withde-ionized water, and dried at 100° C. The catalyst was then calcinedslowly up to 482° C. in air and held there for three hours.

[0065] The calcined catalyst was pelletized in a Carver Press andcrushed to yield particles with a 20/40 mesh size range. Sized catalyst(0.5 g) was packed into a ¼ inch OD tubing reactor in a micro unit forn-hexadecane hydroconversion. The table below gives the run conditionsand the products data for the hydrocracking test on n-hexadecane. Afterthe catalyst was tested with n-hexadecane, it was titrated using asolution of butyl amine in hexane. The temperature was increased and theconversion and product data evaluated again under titrated conditions.The results shown in the table below show that SSZ-63 is effective as ahydrocracking catalyst. Temperature 500° F. (260° C.) 560° F. (293° C.)Time-on-Stream (hrs.) 6.1-7.1 47.6-50.1 WHSV 1.55 1.55 PSIG 1200 1200Titrated? No Yes n-16, % Conversion 100 96.5 Hydrocracking Conv. 93.434.95 Isomerization Selectivity, % 6.6 63.8 Cracking Selectivity, % 93.436.2 C4-, % 8.8 31.85 C5/C4 9.6 12.85 C5 + C6/C5, % 23.34 18.1 DMB/MP0.12 0.07 C4-C13 i/n yield 6.98 4.88 C7-C13 yield 64.84 26.6

Example 21 Argon Adsorption Analysis

[0066] SSZ-63 has a micropore volume of 0.22 cc/gm based on argonadsorption isotherm at 87.6 K recorded on ASAP 2010 equipment fromMicromerities. The low-pressure dose was 3.00 cm³/g (STP) with 15-sequilibration interval. The argon adsorption isotherm was analyzed usingthe density function theory (DFT) formalism and parameters developed foractivated carbon slits by Olivier (Porous Mater., 1995, 2, 9) using theSaito Foley adaptation of the Horvarth-Kawazoe formalism (MicroporousMaterials, 1995, 3, 531) and the conventional t-plot method (J.Catalysis, 1965, 4, 319). Analogous measurements were made with nitrogenusing the Digisorb system.

What is claimed is:
 1. In a process for the reduction of oxides ofnitrogen contained in a gas stream in the presence of oxygen whereinsaid process comprises contacting the gas stream with a zeolite, theimprovement comprising using as the zeolite a zeolite having a moleratio greater than about 15 of an oxide of a first tetravalent elementto an oxide of a second tetravalent element which is different from saidfirst tetravalent element, trivalent element, pentavalent element ormixture thereof and having, after calcination, the X-ray diffractionlines of Table II.
 2. The process of claim 1 wherein said zeolitecontains a metal or metal ions capable of catalyzing the reduction ofthe oxides of nitrogen.
 3. The process of claim 2 wherein the metal iscopper, cobalt or mixtures thereof.
 4. The process of claim 2 whereinthe gas stream is the exhaust stream of an internal combustion engine.